Steps to reproduce:

# Create a project
#  Go to "Project" -> "Asset" section -> right click ->Create ->UI Toolkit -> UI Document ->leave default proposed name -> click "Save"
# Double click on it
# Verify, that "UI Builder" window opens
# Select "VisualElement" in "Containers" window and drag it to the "Hierarchy" window as child object for "NewUXMLTemplate.uxml"
# Observe "Inspector" section

Actual result: User gets overlapping. Added screenshot in the "Attachments" section.

Expected result: User shouldn't get this.

(Old list of steps to reproduce as reported by user):

# Create a project
#  Go to "Project" -> "Asset" section -> right click ->Create ->UI Toolkit -> UI Document ->leave default proposed name -> click "Save"
# Double click on it
# Verify, that "UI Builder" window opens
# Drag "UI Builder" tab next to "Game" tab
# Select "VisualElement" in "Containers" window and drag it to the "Hierarchy" window as child object for "NewUXMLTemplate.uxml"
# Click "+" in StyleSheets section and create new USS file
# Select "Label" in "Controls" section and drag into "Hierarchy" window as child for "VisualElement"
# In "Inspector" section lets add ".header" class in "Style Class List"
# Verify, that it becomes added
# Let's delete "Label" from "Hierarchy" section
# Let's select "VisualElement"
# Observe "Inspector" section

Actual result: User gets overlapping. Added screenshot in the "Attachments" section.

Expected result: User shouldn't get this.

Reproducible with: 2023.1.0a21, 2023.1.0b7, 2023.2.0a5.

Not reproducible with: 2021.3.20f1, 2022.2.9f1, 2020.3.46f1 (functionality not available).